The effects of adenosine are mediated through at least four specific cell membrane receptors so far identified and classified as receptors A1, A2A, A2B and A3 belonging to the G protein-coupled receptor family. The A1 and A3 receptors down-regulate cellular cAMP levels through their coupling to Gi proteins, which inhibit adenylate cyclase. In contrast, A2A and A2B receptors couple to Gs proteins that activate adenylate cyclase and increase intracellular levels of cAMP. Through these receptors, adenosine regulates a wide range of physiological functions.
Several preclinical studies demonstrate the usefulness of adenosine A2A receptor antagonists to treat neurodegenerative diseases, mainly Parkinson's, Huntington's or Alzheimer's diseases (Trends in Neurosci. 2006, 29(11), 647-654; Expert Opinion Ther. Patents, 2007, 17, 979-991; Exp. Neurol. 2003, 184(1), 285-284; Prog. Brain Res, 2010, 183, 183-208; J. Alzheimer Dis. 2010, Suppl 1, 117-126; J. Neurosci. 2009, 29(47), 14741-14751; Neuroscience, 2010, 166(2), 590-603; J. Pharmacol. Exp. Ther. 2009, 330(1), 294-303; Frontiers Biosci. 2008, 13, 2614-2632).
Besides the welcome utility of A2A receptor antagonists to treat neurodegenerative diseases, those compounds have been considered for complementary symptomatic indications. These are based on the evidence that A2A receptor activation may contribute to the pathophysiology of a range of neuropsychiatric disorders and dysfunctions such as depression, excessive daytime sleepiness, restless legs syndrome, attention deficit hyperactivity disorder, and cognitive fatigue (Neurology, 2003, 61(11 Suppl 6), S82-S87; Behav. Pharmacol. 2009, 20(2), 134-145; CNS Drug Discov. 2007, 2(1), 1-21).
Some authors suggest the application of A2 antagonists for the treatment of diabetes (WO1999035147; WO2001002400).
Other studies suggest the involvement of A2a adenosine receptors in wound healing or atrial fibrillation (Am J Path, 2007, 6, 1774-1778; Arthritis & Rheumatism, 2006, 54(8), 2632-2642).
For this reason, there is an increasing interest in the discovery of novel, potent and selective adenosine A2a antagonists. Some of the potent adenosine A2a antagonists discovered in the past by the pharmaceutical companies, have advanced into clinical trials showing positive results and demonstrating the potential of this compound class for the treatment of neurodegenerative disorders like Parkinson's, Huntington's or Alzheimer's disease, but also in other CNS related diseases like depression, restless syndrome, sleep and anxiety disorders (Clin. Neuropharmacol. 2010, 33, 55-60; J. Neurosci. 2010, 30(48), 16284-16292; Parkinsonisn Relat. Disord. 2010, 16(6), 423-426; 1 Expert Opinion Ther. Patents, 2010, 20(8), 987-1005; Current Opinion in Drug Discovery & Development, 2010, 13(4), 466-480 and references therein; Mov. Disorders, 2010, 25(2), S305).
The present invention relates to novel 4-amino-pyrimidine derivatives as potent antagonists of the adenosine A2a receptor. There are reports in the literature showing that 4-aminopyrimidines of formula:

Wherein R1 and R3 can be heteroaryl groups and R2 can be a hydrogen atom or a substituted alkyl chain are potent adenosine A2a receptor antagonists (e.g. WO 2005058883 A1; WO2008116185).
However, we surprisingly found that by introducing an electron-withdrawing substituent at the position 5 of the pyrimidine-ring the potency of the compounds as adenosine A2a antagonists can be considerably increased in comparison to the parent unsubstituted derivatives, as illustrated by the following examples:
